This invention relates to transmissions for motor vehicles having two powered axles and, more particularly, to transmissions for vehicles having an engine mounted transverse to the direction of travel and having a transmission with its centerline parallel to the engine shaft.
In such known transmissions, as described, for example, in German Offenlegungsschrift No. 33 17 247, one driven axle of the vehicle is powered by an output drive gear which also serves as a flywheel for a centrifugal or injection lubricating system for the transmission. To power the second driven axle of the vehicle, the drive system contains an angle drive connected to the transmission output drive gear by a connecting shaft which may be a hollow shaft. The housing for the angle drive is arranged on the side of the transmission housing adjacent to the output drive gear connection for the transmission and a shaft support for the connecting shaft leading from the output drive gear to the angle drive preferably consists of tapered roller bearings mounted in a partition between the two housings. Both housings are filled with a supply of lubricant for centrifugal or injection lubrication of the gear parts contained therein.
The lubricant supply for a centrifugal and injection lubricated transmission should be so proportioned that adequate lubrication is provided in each phase of operation while, at the same time, the quantity of lubricant used is limited to the minimum actually required so as to inhibit heating resulting from agitation that would impair the lubricating function of the lubricant. Problems can arise from this, particularly in the case of high-power angle drives, i.e., angle drives transmitting a large amount of power.
In the first place, the interior volume of the angle drive is relatively small, compared to that of the transmission, and hence its lubricant content is correspondingly small. In the second place, a high-power transmission always involves a correspondingly high evolution of heat which has to be removed by the lubricating oil. For reasons of space, an effort is maintained to provide the greatest compactness, economy of space and small volume in the design of the angle gear but, at the same time, the oil supply in the comparatively confined angle gear housing cannot easily be replenished. Any additional oil would escape through the bearings for the connecting shaft into the transmission housing, where the oil level when the vehicle is stationary is generally lower than the shaft bearings.